Hanami ko, a Japanese go term that literally means flower-viewing ko, is a unilaterally favorable ko fight. Winning this fight will inflict major damage on the other side, whereas losing will result in only a tiny loss for your side, often half a point.
In general, your gain from a hanami ko is either the large follow-up from the ko, or, more commonly, the follow-up from a ko threat which your opponent has no choice but to ignore.
Sometimes rendered as picnic ko, hanami ko evokes the carefree nature of the Japanese tradition of hanami (lit. flower viewing), the viewing of the spring blossoms, often involving food, drink, and partying.
The Chinese terms 看花劫 (kàn huā jié) literally means flower viewing ko. The term 无忧劫 (wú yōu jié) literally means ko with no worries.
After , would live, but and then risk everything in a two stage hanami ko for Black.
In the diagram, starts a hanami ko for White. Even if Black wins the ko the best he can do is connect at . White, on the other hand, may win the ko by capturing with a, destroying Black's corner. In this example, White's follow-up gain is relatively small; in other hanami kos, it could be dozens of points or involve the life and death of major groups.
More on the /Discussion page.